December 6, 2016 at 6:29PM, Edited December 6, 6:31PM

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Does 4k Make Up for a Mediocre Lens?

I've been using the a6300 for a few months now and am happy with the results I am getting from the 16-50 kit lens. I also bought the 18-105 for further reach. In the resolution department, I don't think I've gained much with the 18-105. I've used my Zeiss 35mm on the camera also and am not particularly blown away and usually just use the 18-105. On My Canon and Blackmagic bodies, there is a night and day difference when going from Canon/Panasonic native lenses to the Zeiss. But on the A6300, no discernible difference in resolution. I'm pretty sure there is a difference if I pixel peep but don't care enough to. Are the 16-50 and 18-105 just damn good lenses or does the 4K make up for their shortcomings?

6 Comments

My favorite photo lens review website is : http://www.lenstip.com/lenses_reviews.html

I always check to see how a lens is rated before investing in new glass, especially with how the lens performs at the widest apertures. Both of your Sony lenses are reviewed at this website.

December 7, 2016 at 12:30AM

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Guy McLoughlin
Video Producer
32741

The sensor can only capture what the lens lets it see. So if a lens looks soft on an HD camera, the only difference with a UHD camera will be that it takes 4x as long to render.

To start, sharpness and resolution are not the same thing. The MTF (modulation transfer function) of a lens can help shed some light on the subject. If the MTF of a lens is 80% contrast at 50 lines per mm and 50% at 80, the resolution is considered to be about 80 lines per mm. The most the camera can resolve is is 50% at 80 lines per mm (960 lines total if you're using a BMPCC) but it's likely less due to the camera's own optical block (or film emulsion).
Now that's not the end of the story, there could be another lens that resolves 900 lines on your camera but looks sharper because the MTF may be 80% at 65 lines per mm. The resolution is technically less but contrast is flatter up the the limit of the lens's MTF so it's sharper to the eye. I've seen HD cameras with 8MP sensors or whatever but only resolved 300 lines because the lenses were junk. Now a few things to remember: zoom lenses almost always look softer than prime lenses because they have many more elements, which scatter light and reduce the MTF in finer details. Longer focal lengths also tend to look softer because you are taking source that's limited in resolution by the front optics and making them larger.

I suspect there's more discernible difference between lenses with your BM because it doesn't have an optical low-pass filter, so alias distortion is rampant on it, giving the illusion of more fine details. There may also be something not quite right about the resize of your A6300. I continually harp on still cameras not being optimal for video because they are still cameras first. Video functions are added for convenience but they aren't designed for that job and thus suffer issues the still shots don't have.

December 7, 2016 at 7:25AM, Edited December 7, 7:55AM

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Thanks for your input. Sharpness (not resolution) is indeed what I meant.

December 8, 2016 at 9:02AM

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Don Way
Writer/Director of Photography
1039

The answer is no, 4k makes lenses issue more visible so a cheap lense will look worst in 4k. BUT Sony lenses looks great on the a6300 because there is in body lens compensation, the images are transformed inside, aberrations are removed, distortion is compensated and in the end it looks like the lense is optically perfect. If you want you can disable it in the menu and your lenses will look bad again :-)
It's a great feature it means you can get great image quality from cheaper made lenses. I also have the a6300 and the 18-105 and this combo works very, very well, I leave my canon lenses at home more and more.

December 10, 2016 at 12:39PM, Edited December 10, 12:44PM

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AvdS
1179

Ahhh. For some reason, I thought that the A series cameras only corrected photos in camera. I had no idea they corrected video also. I guess that's the reason I haven't experienced the pin cushioning in the 18-105 that I've read about. I'm definitely going to turn the feature off just to see how good/bad these lenses really are, just out of curiosity. And then I'm going to turn the feature back on of course haha.

December 11, 2016 at 9:26PM

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Don Way
Writer/Director of Photography
1039

I think it depends more on the sensor than anything else. I have an A7s and T3i, both are 1080p. Using the same lenses on both cameras, it is very clear that the A7s image is better than the T3i. I also haven't seen that much difference in image quality when using a good lens and bad lens on the T3i.

So in other words, I think an A7s with an okay lens will have more detail (and to my eyes) look better than a T3i with a great lens.

December 10, 2016 at 3:23PM

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Gareth Ng
Cinematographer
730

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